The present invention relates to a hydraulic platform lift, in particular a motorcycle platform lift, comprising a parallelogram chassis, in which on one of the two parallel lifting arms a hydraulic cylinder, supported on the sub-frame, engages the one lifting arm at an articulation point on a projection directedly downwardly therefrom to beneath the pivot axis of the one lifting arm on the sub-frame, in order to make available a favorable lever arm between the articulation point and the pivot axis of the one lifting arm for the force transmission of the hydraulic cylinder.
A platform lift known from prior art is depicted in FIGS. 2.1 to 2.3. The pressure force of the hydraulic cylinder which, in platform lifts of the above-described type, can be up to approximately 3 t, is here completely shunted into the sub-frame. This sub-frame as well as also the particular lifting arm must be dimensioned correspondingly thick in order to be able to absorb these forces. This leads to an unfavorable intrinsic weight/lifting-force ratio which is the reason why these lifts as a rule are reserved as stationary equipment for workplaces.
Furthermore, a factor affecting the intrinsic weight/lifting-force ratio disadvantageously is that the second lifting arm is pulled by the lifting arm acted upon by the hydraulic cylinder over the top-frame. This construction would by necessity lead to jamming of the parallelogram chassis with large loads to be lifted and for reasons of reduction of the intrinsic weight thinly dimensioned structural components of the platform lift.
From EP 0 047 976 A2 and U.S. Pat. No. 2,920,773 lifting devices are known in which the hydraulic cylinder supported on the sub-frame engages the sub-frame at an articulation point beneath the pivot axis of the one lifting arm on the sub-frame. For this purpose, this lifting arm comprises in this region a projection directed downwardly. Through this projection a very favorable lever arm for the transmission of the lifting force of the hydraulic cylinder onto the lifting arm is given.
Known platform lifts of the type under consideration here therefore for the reasons listed above have an intrinsic weight between approximately 140 to more than 200 kg with the lifting capability being approximately 400 kg.